1. Field of the Present Invention
The present invention relates to a display device in which a light emitting element is provided in a display panel.
2. Description of the Related Art
In recent years, in the field of a display device displaying an image, a display device using, as a light emitting element of a pixel, a current drive type optical element, for example, an organic EL (electro luminescence) element, in which light emission luminance is varied according to the value of a flowing current has been developed, and progressively commercialized. Unlike a liquid crystal element or the like, the organic EL element is a self-luminous element. Thus, in a display device using the organic EL element (organic EL display device), since a light source (backlight) is not necessary, thinning and high luminance are realized in comparison with a liquid crystal display device in which the light source is necessary. In particular, in the case where the active matrix method is used as a driving method, it may be possible to light and hold each pixel, and this enables low power consumption. Therefore, the organic EL display device is expected to become the mainstream of a flat panel display in the next generation.
However, in the organic EL element, an element is deteriorated in accordance with the amount of a flowing current, and there is an issue that the luminance is reduced. Thus, in the case where the organic EL element is used as a pixel in the display device, the state of deterioration may be varied for each pixel. For example, in the case where information such as a time and a display channel is displayed with a high luminance in the same place for a long time, deterioration of only the pixels in that section is accelerated. As a result, in the case where a video having a high luminance is displayed in the section including the pixels whose deterioration is accelerated, a phenomenon called “seizure” is generated such that only the section of the pixels whose deterioration is accelerated is darkly displayed. Since the seizure is irreversible, when the seizure is once generated, it is not eliminated.
A great number of methods for preventing the seizure have been proposed so far. For example, in Japanese Unexamined Patent Publication No. 2002-351403, the method in which a dummy pixel is provided in a region other than a display region, and the deterioration degree of the dummy pixel is estimated by detecting a terminal voltage when the dummy pixel emits light, thereby correcting a video signal by utilizing that estimation is disclosed. Further, for example, in Japanese Unexamined Patent Publication No. 2008-58446 and International Publication WO 2006/046196, the methods in which an optical sensor is disposed in each display pixel, and a video signal is corrected by utilizing a light reception signal output from the optical sensor are disclosed.